This invention relates to a process for the separation of solids containing residues from a product. The invention particularly relates to a process for the hydrogentation of coal at elevated temperatures and pressures, wherein various product fractions such as the lower boiling product fractions are separated, and specifically wherein a solid containing residues fraction is separated from a fraction containing the higher boiling product components. The separation process comprises pressure release and the subsequent sepration of the phases of the product fraction.
In the process for the catalytic hydrogenation of coal under elevated pressures and temperatures, a product is obtained which comprises gaseous and liquid components including hydrogen, lower boiling hydrocarbon components, steam, liquid ditillation oils, as well as carbon, unreacted coal residues, catalyst particles, and sticky asphalt-like substances. The separation of the gaseous and lower boiling hydrocarbon components from the product is relatively simple. However, difficulties are encountered in the separation of the higher boiling liquid distillation oils from the remaining solids containing hydrogenation residues and sticky asphalt like substances. In convention distillation procedures and equipment for the separation of the distillation oils from the residues, considerable incrustations and depositions of sticky asphalt-like substances are formed on the equipment in relatively short periods of time. In addition, the asphalt-like substances have coking tendencies and during the distillation process can be coked, whereby the distillation equipment is further fouled.
It has been previously proposed to eliminate the distillation procedures and equipment for the separation of the distillation oils from the solids containing residues, and to use a pressure release evaporation procedure, whereby the released distillation oils in the form of gaseous vapors are subsequently removed. This evaporation procedure involves the release of the high pressure and temperature (e.g. about 250 bar and 450.degree. C.) from the product fraction containing the solids containing residues and the distillation oils. The pressure release of the fraction to the ambient atmospheric pressure is accomplished by means of throttle valves, and the evaporated gaseous vapors fraction is subsequently submitted to phase separation in conventional separating means. By this procedure, it is possible to remove the major portion of the distillation oils in the form of gaseous vapors, and to obtain a concentrated remaining fraction of the predominantly solids containing hydrogenation residues.
Although the above evaporation procedure appears to attain the desired result, there are considerable disadvantages encountered. Particularly bothersome is the fact that the throttle valves become inoperative in a relatively brief period of operating time due to the large differentials of pressures handled and also due to the pressure of the solids components in the fraction being handled.